In this type of design which is well known, the electromagnetic motor includes a rotor with which a permanent magnet is associated, such rotor being mounted for rotation by means of pivots within the cage.
To this end, such cage, which is formed in the known arrangements of a non-magnetic metallic material such as brass, includes a bottom and a cover in which are respectively formed a first and second guidance orifice while the rotor includes, at its ends, two pivots respectively engaged in said orifices.
Such cage, which exhibits a form generated by rotation, is provided with a cylindrical body the wall of which is integral with the bottom and supports the cover which is inserted and fixedly maintained therein.
In order to permit mechanical coupling between teeth which are formed on the rotor and an exterior mechanism to be driven, such cage includes, in the bottom mentioned above, a cut-out which extends axially in the wall of the cylindrical body and which leaves the place free in order to accommodate the exterior wheel of the mechanism to be driven.
This type of electromagnetic stepping motor is used in timepieces.
For construction reasons, it has been sought to form the cage which has just been described from a material other than metallic material.
Thus, it has been possible to define that use of synthetic materials was more favourable in this application, in particular in lowering the manufacturing cost.
Nevertheless, the forming of such a cage of synthetic material and its assembly on the motor causes numerous problems to become apparent.
Effectively, known metal cages offer a resistance to lateral stresses which is such that such cages can be driven (force mounted) within the interior of the stator which includes a circular orifice provided to this end.
This type of driving cannot be envisaged with cages formed of synthetic material because of their low resistance.
Thus, the present invention has as purpose to provide an electromagnetic motor including a cage of synthetic material which can be anchored in a stator of the motor in a reliable manner without subjecting the body of the cage to stresses likely to bring about its deformation.